This invention relates to a tape carrier provided with bumps (or a bump-attached tape carrier), to the manufacturing method thereof, and to the method of manufacturing a semiconductor device wherein a semiconductor chip is mounted on a bump-attached tape carrier.
In order to meet various needs for an electronic instruments such as the miniaturization, weight-saving, speed-up, improved functionality thereof, etc., various types of semiconductor packages have been developed. As one of such semiconductor-packaging techniques, there has been developed a packaging technique of a so-called tape carrier system wherein a semiconductor chip is bonded via a solder bump to a metal pattern formed on an insulating film, this tape carrier system being especially intended to meet the needs for an increasing number of pins due to an increasing integration of semiconductor chips and for the miniaturization of devices.
One example of packaging techniques utilizing this tape carrier system is disclosed in Japanese Patent Unexamined Publication No. H/8-64636. As shown in FIG. 1, according to this packaging technique, a metal layer 2 is formed on a polyimide tape 1, and solder bumps 3 are formed on the metal layer 2. The solder bumps 3 are then thermally bonded with metal pads 6 formed, in conformity with the solder bumps 3, on one main surface of an electronic device (semiconductor chip) 4. The tape carrier carrying electronic devices 4 in this manner is subsequently cut off to obtain discrete electronic devices.
Since a thin transparent polyimide tape is employed in this tape carrier system, this tape carrier system is advantageous in that any stress to be laid upon the solder-bonded portions can be alleviated even at the occasion of heat cycling and that the solder bumps can be observed from the reverse surface of the tape.
The solder bumps are generally formed by means of a cream solder printing method or a solder ball-transferring method. However, since the solder bumps are adhered on a conductor circuit in a molten state thereof, these solder bumps 3 are forced to be a spherical figuration due to the surface tension acting on the droplet of solder as shown in FIG. 1. This spherical solder bump however gives rise to the problem that when the solder bumps is densified or the distance between solder bumps is shortened, a solder bridge may to be formed as a semiconductor chip is mounted on these solder bumps.
For example, when the bonding height of the solder bumps is set to 50 .mu.m in a solder bump bonding where the solder bumps are formed on a tape at a pitch of 100 .mu.m (50 .mu.m in pad width/50 .mu.m in interval), the diameter of solder bump becomes as large as 70 .mu.m. Therefore, the distance between the solder bumps becomes as short as 30 .mu.m.
When the distance between the solder bumps declines to such an extent in the employment of spherical solder bumps, a solder bridge may be formed as a semiconductor chip is mounted on these solder bumps. Moreover, there is another problem that the charging of an under-fill resin may become difficult.
Further, when a flux is coated on the tape carrier by means of the ordinary method on the occasion of bonding the solder bumps of the tape carrier to the metal pad of a semiconductor chip, not only the solder bumps but also a conductor pattern is covered with the flux, so that the solder may flow out to the conductor pattern on the occasion of fusing the solder. As a result, the height of the bumps may become further lower, thus making it difficult to secure a gap between the semiconductor chip and the tape carrier. Further, the solder may become spherical, thus inviting the formation of a solder bridge as mentioned above.
Additionally, when a flux of high viscosity having a high content of solid matter is employed with a view to temporally fixing a semiconductor chip, a residue of flux may persist between the semiconductor chip and the tape carrier, thus making it necessary to wash out the residue of flux in a subsequent step.